The reaction of isocyanates with amines is known in the art and is an extremely fast reaction. It has only been recently that higher molecular weight diamines could be made to react with diisocyanates in a controlled fashion. Work in this area led to the Reaction Injection Molding (RIM) process for the preparation of polyurea plastics.
Reaction of polyisocyanates with polyamines that were soluble or partially soluble in water has often led to gel formation though it might have been expected there would be advantages to carrying out the reaction in water, in that the water would serve as a heat sink.
In contrast to isocyanate-amine reaction, the reaction of alcohol-isocyanate proceeds at a slower rate. In general, the industrial application of polyurethane synthesis employs a catalyst, such as an organotin compound. The isocyanate polymers prepared from polyol and isocyanate are well-known and used widely in commercial processes. (see J. H. Saunders and K. C. Frisch, High Polymer Vol. XVI, polyurethanes: Chemistry and Technology (part 1) Interscience publishers (1962)).
The preparation and uses of polyol-isocyanate prepolymers can be found in references in the art.
Chung et al. disclose in U.S. Pat. No. 4,590,254 a poly(urethane-urea) which is prepared by reverse addition of an isocyanate-terminated prepolymer to an organic medium containing a chain extender such as hydrazine.
In U.S. Pat. No. 4,617,349, Nasu et al. disclosed a urethane resin composition which comprises a polyisocyanate component having from 20/80 to 80/20 of a weight ratio on a solid basis of an .alpha., .alpha., .alpha.', .alpha.'- tetramethyl-xylylene diisocyanate derivative to a hexamethylene diisocyanate derivative and (b) an acrylic polyol.
In U.S. Pat. No. 4,614,787 there is disclosed a method for preparing a wound dressing having a drug dispensed throughout a polyurethane matrix that is the reaction product of: (a) an isocyanate-terminated prepolymer formed by the reaction of isophorone diisocyanate and a macroglycol and (b) a monomer containing hydroxyl and vinyl groups.
In U.S. Pat. No. 4,611,043 there is disclosed a coating composition prepared from (a) an isocyanate terminated prepolymer which comprises the reaction product of at least one polyurethane-forming reagent containing a plurality of isocyanate groups and at least one polyfunctional polyhydric alcohol and (b) dicyclopentenyl alcohol.
In U.S. Pat. No. 4,605,504 is disclosed a method for production of the polyetherurethane particles by forming a prepolymer and subjecting the dissolved prepolymer to the presence of a 2-methylpiperazine suspension to allow polymerization to occur.
The above prepolymers were generally prepared from polyol and diisocyanate using tin catalyst and elevated reaction temperatures.
U.S. Pat. No. 4,609,718, discloses a coating composition consisting essentially of a linear acrylate-terminated polyurethane oligomer, including urea groups, introduced by the presence in the oligomer of a reaction product with an isocyanate functionality of about 30% to about 90% by weight of the acrylate-terminated oligomer of a polyoxyalkylene diamine having a molecular weight in the range of from about 1000 to about 8000. The mentioned isocyanate-terminated polyoxyethylene diamine was a high-molecular diamine with reactions using dibutyl tin dilaurate catalyst at elevated temperature.
Discriptions and uses of "blocked" isocyanates can be found in the following applications:
U.S. Pat. No. 4,495,229 discloses a polyurethane, one component, heat-cured coating which is stable in storage and is hardened above a temperature of about 120.degree. C. The coating comprises a polyol and a blocked isocyanate.
In an article titled "Blocked Isocyanates in Coatings" by Mobay Chemical Corp., presented at "Water-Borne and Higher Solids Conference", Feb. 5-7, 1986, New Orleans, La., there are outlined commercial areas where specific products based on blocked polyisocyanates exhibit possible uses.
It would be a distinct advance in the art if a novel polyoxyalkylenediamine containing isocyanate groups could be prepared without a metal catalyst wherein the hardness of cured coatings was controllable and storage stability was improved. It would be an advance in the art if this could be accomplished by a method which avoided gel formation. In addition, it would be desirable if the products were colorless and the process could be carried out at low temperatures. Uses of compositions with such desirable properties in coatings would be apparent.